Brake Pad Deposits

[Stanky]

Hello all,

 

The Saab makes droning noises from the front passenger side when braking from speed - 50+MPH or so, braking performance isn't affected and it doesn't pull to either side at all. Looking at the disc is has some browny lumpy deposit on it (the other 3 are all clean metal) which i suspect is brake pad grot.

 

I have a few questions regarding this

 

1. Should I worry about it?

2. How can i remove it? I have tried taking it up to 60mph and braking sharply several times which has cleaned some of it off, but there is a stubborn layer which doesn't seem to want to come off

3. Could it be something else?

 

The car went through an MOT fine with this affliction and to my knowledge nothing was said about it, but since the braking performance wasn't adversely affected, the MOT people probably didn't care too much.

 

There is lots of meat on the pads and the disc doesn't seem to be worn or warped - I've had warped discs on a golf before and the sensation is different, this is more like a droning noise than a judder that you get with warped discs.

 

I'd rather not have to replace the discs and pads, but equally I'd rather not lose all braking and crash into a tree at 70mph for the sake of spending a few pounds.

 

Assuming my hypothesis is right, can the discs be cleaned using a wire brush or abrasive sandpaper in situ?

 

[RayMK]

I've occasionally seen this type of marking, but usually on newly replaced brake shoes (drum brakes).  It's a variation on 'brake glazing' where the heat causes some of the resin to leach out and coat the rotating bits.  Yes, light abrasion will remove it without detriment, provided you don't breath the dust.  Asbestos is unlikely in modern pads, but any industrial type dust should be regarded with due caution.

[Vantman]

You have a PM.

[overrun]

Grinder with a wire knot wheel, imo.

[SOUL]

I'd personally get them stinking hot to burn off the glaze.  I had EBC Greenstuff on the old Fabia and unless you braked like a pillock regularly they would glaze.  EBC's own instructions for bedding in, is something like brake from 70mph hard to stop 10 times in a row.  Makes them stink, but boy do Greenstuff pads bite afterwards.  Still it gets you used to your ABS performance, if you have it! LOL

[Pillock]

My Saab does this too, I've noticed the discs are quite scored even though there's plenty of meat on the pads so it's not like they're down to the backing plates.

 

I remember on Wheeler Dealers, Ed used some sort of lathe type thing that bolted to the hub and rotated the disc around, grinding off a lip. However, this was a Porsche and the discs were megabucks and lipped, not worn out.

I'm going to just spend £60 on a new set of discs and pads and be done with it.